md_browser: Implement Gitiles blocks notation.

tools/md_browser/md_browser.py

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Simple Markdown browser for a Git checkout."""
 from __future__ import print_function
 
 import SimpleHTTPServer
 import SocketServer
 import argparse
@@ skipping 56 matching lines @@
     elif path.lower().endswith('.md'):
       self._DoMD(path)
     else:
       self._DoUnknown()
 
   def _DoMD(self, path):
     extensions = [
         'markdown.extensions.fenced_code',
         'markdown.extensions.tables',
         'markdown.extensions.toc',
+        'gitiles_ext_blocks',
     ]
 
     contents = self._Read(path[1:])
     md_fragment = markdown.markdown(contents,
                                     extensions=extensions,
                                     output_format='html4').encode('utf-8')
     try:
       self._WriteTemplate('header.html')
       self.wfile.write(md_fragment)
       self._WriteTemplate('footer.html')
@@ skipping 13 matching lines @@
     with codecs.open(path, encoding='utf-8') as fp:
       return fp.read()
 
   def _WriteTemplate(self, template):
     contents = self._Read(os.path.join('tools', 'md_browser', template))
     self.wfile.write(contents.encode('utf-8'))
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))